Device for arresting the propagation of a buckle in a double-walled pipe

Abstract

Device for arresting the propagation of a buckle in a double walled pipe. The device comprising an outer pipe wall having a defined external diameter and placed around an inner pipe wall, defining an annular space between the said outer and inner walls; providing predetermined regions in the annular space which are bounded between two sealing blocks with radially opposed faces which are in contact with the outer and inner pipes; placing a curable compound in each region and curing it the length of each region is at least equal to 0.5 times the external diameter of the outer wall.

1. A method of manufacturing a reelable double-walled rigid pipe for underwater transportation of fluids, wherein the pipe comprises an inner flow pipe, the interior of which defines a passage for transporting the fluid, an outer carrier pipe which surrounds the flow pipe, and a plurality of longitudinally spaced separating elements between the inner and outer pipes which define an annular space therebetween, the method comprising:
 selecting dimensions and properties of the inner pipe and the carrier pipe according to an intended fluid transportation application, and an intended pipeline location, and to have suitable mechanical properties which permit the double walled pipe to be plastically deformed for reeling on a vessel reel and then straightened while being laid offshore; 
 assembling a double walled pipe using the selected carrier and flow pipes, and the separating elements; and 
 forming a device within the double-walled pipe for arresting longitudinal propagation of buckling of the outer carrier pipe, by:
 placing at least one pair of sealing blocks axially spaced apart between the outer wall of the flow pipe and the inner wall of the carrier pipe; 
 the sealing blocks having a first circumferentially extending face and a second radially opposite face, the faces being dimensioned to be in contact respectively with the outer and inner walls of the flow pipe and the carrier pipe, to define a sealed annular region within the annular space; 
 spacing the sealing blocks so that the axial length of the annular region is at least equal to 0.5 times the external diameter of the carrier pipe, but occupies substantially less than the entire annular space; 
 placing a curable compound in the annular region; 
 curing the compound in the annular region; and 
 winding the pipe on a reel after placing and curing the compound. 
 
 
   
   
     2. The method of  claim 1 , wherein the axial length of the annular region is in the range of 0.5 to 2 times the external diameter of the carrier pipe. 
   
   
     3. The method of  claim 1 , further comprising installing a rigid bearing plate to bear against at least one lateral side of each of the sealing blocks. 
   
   
     4. The method of  claim 3 , wherein the bearing plate has a radial dimension that is less than the radial dimension of the annular space. 
   
   
     5. The method of  claim 4 , wherein:
 the bearing plate is fastened to the outer wall of the flow pipe, 
 the bearing plate has a radially outer free edge and is so dimensioned as to define a gap between the free edge of the bearing plate and the inner wall of the carrier pipe. 
 
   
   
     6. The method of  claim 5 , wherein the bearing plate is made of metal. 
   
   
     7. The method of  claim 1 , wherein the curable compound is an epoxy resin. 
   
   
     8. The method of  claim 1 , further including the steps of:
 providing an injection orifice through the wall of the carrier pipe into the annular region; and 
 injecting the curable compound into the annular region through the orifice. 
 
   
   
     9. The method of  claim 8 , wherein the curable compound is a thermosetting compound. 
   
   
     10. The method of  claim 8 , wherein the curable compound is curable at room temperature. 
   
   
     11. The method of  claim 1 , further comprising the steps of:
 reeling the rigid pipe onto a reel after assembly but before placing the curable compound in the annular region; 
 unreeling the rigid pipe from the reel, 
 placing the curable compound the annular region after the pipe has been unreeled, and 
 heating the annular region to accelerate the curing of the curable compound. 
 
   
   
     12. The method of  claim 11 , wherein the annular region is heated by passing it through a heater. 
   
   
     13. The method of  claim 12 , further comprising the step of straightening the pipe before heating the annular region to cure the compound. 
   
   
     14. The method of  claim 13 , wherein:
 the pipe is straightened in straighteners in a pipe laying vessel; and 
 the annular region of the pipe is heated in a heater mounted after the straightener on the vessel along the path of movement of the pipe: and 
 further including the step of moving the pipe from the reel through the straighteners and past the heater. 
 
   
   
     15. The method of  claim 13 , wherein the curable compound is placed in the annular region after the pipe has been straightened. 
   
   
     16. The method of  claim 1 , wherein the curable compound has a pot life in the range of a few minutes to a few weeks. 
   
   
     17. A method of  claim 1 , wherein the step of assembling the double walled pipe further comprises including therein a plurality of pairs of axially spaced sealing blocks, thereby defining a plurality of annular regions, the totality of the axial lengths of the plurality of annular regions occupying substantially less than the entire annular space. 
   
   
     18. A method of manufacturing a reelable double-walled rigid pipe for underwater transportation of fluids, wherein the pipe comprises an inner flow pipe, the interior of which defines a passage for transporting the fluid, an outer carrier pipe which surrounds the flow pipe, and a plurality of longitudinally spaced separating elements between the inner and outer pipes which define an annular space therebetween, the method comprising:
 selecting dimensions and properties of the inner pipe and the carrier pipe according to an intended fluid transportation application, and an intended pipeline location, and to have suitable mechanical properties which permit the double walled pipe to be plastically deformed for reeling on a vessel reel and then straightened while being laid offshore; 
 assembling a double walled pipe using the selected carrier and flow pipes, and the separating elements; and 
 forming a device within the double-walled pipe for arresting longitudinal propagation of buckling of the outer carrier pipe, by:
 placing at least one pair of sealing blocks axially spaced apart between the outer wall of the flow pipe and the inner wall of the carrier pipe; 
 wherein each of the sealing blocks is comprised of a material which is radially deformable when compressed axially and axially compressing the sealing blocks to conform the radially outer margins thereof to the shape of the respective inner and outer walls of the carrier pipe and the flow pipe; 
 the sealing blocks having a first circumferentially extending face and a second radially opposite face, the faces being dimensioned to be in contact respectively with the outer and inner walls of the flow pipe and the carrier pipe, to define a sealed annular region within the annular space; installing a rigid bearing plate to bear against at least one lateral side of each of the sealing blocks, fastening the bearing plate to the outer wall of the flow pipe, wherein the bearing plate has a radial dimension that is less than the radial dimension of the annular space, the bearing plate has a radially outer free edge and is so dimensioned as to define a gap between the free edge of the bearing plate and the inner wall of the carrier pipe; 
 spacing the sealing blocks so that the axial length of the annular region is at least equal to 0.5 times the external diameter of the carrier pipe, but occupies substantially less than the entire annular space; 
 placing a curable compound in the annular region; and 
 curing the compound in the annular region. 
 
 
   
   
     19. A method of manufacturing a reelable double-walled rigid pipe for underwater transportation of fluids, wherein the pipe comprises an inner flow pipe, the interior of which defines a passage for transporting the fluid, an outer carrier pipe which surrounds the flow pipe, and a plurality of longitudinally spaced separating elements between the inner and outer pipes which define an annular space therebetween, the method comprising:
 selecting dimensions and properties of the inner pipe and the carrier pipe according to an intended fluid transportation application, and an intended pipeline location, and to have suitable mechanical properties which permit the double walled pipe to be plastically deformed for reeling on a vessel reel and then straightened while being laid offshore; 
 assembling a double walled pipe using the selected carrier and flow pipes, and the separating elements; and 
 forming a device within the double-walled pipe for arresting longitudinal propagation of buckling of the outer carrier pipe, by:
 placing at least one pair of sealing blocks axially spaced apart between the outer wall of the flow pipe and the inner wall of the carrier pipe, wherein each of the sealing blocks is comprised of a material which is radially deformable when compressed axially, and axially compressing the sealing blocks to conform the radially outer margins thereof to the shape of the respective inner and outer walls of the carrier pipe and the flow pipe, 
 the sealing blocks having a first circumferentially extending face and a second radially opposite face, the faces being dimensioned to be in contact respectively with the outer and inner walls of the flow pipe and the carrier pipe, to define a sealed annular region within the annular space; 
 spacing the sealing blocks so that the axial length of the annular region is at least equal to 0.5 times the external diameter of the carrier pipe, but occupies substantially less than the entire annular space; 
 
 at the time of assembly, each sealing block has a radial dimension less than the radial dimension of the annular space; and
 subsequent to assembly, further including the step of radially expanding the sealing block to bring its radially opposite faces into tight contact with the outer wall of the flow pipe and the inner wall of the carrier pipe; 
 placing a curable compound in the annular region; and 
 curing the compound in the annular region. 
 
 
   
   
     20. A method of manufacturing a reelable double-walled rigid pipe for underwater transportation of fluids, wherein the pipe comprises an inner flow pipe, the interior of which defines a passage for transporting the fluid, an outer carrier pipe which surrounds the flow pipe, and a plurality of longitudinally spaced separating elements between the inner and outer pipes which define an annular space therebetween, the method comprising:
 selecting dimensions and properties of the inner pipe and the carrier pipe according to an intended fluid transportation application, and an intended pipeline location, and to have suitable mechanical properties which permit the double walled pipe to be plastically deformed for reeling on a vessel reel and then straightened while being laid offshore; 
 assembling a double walled pipe using the selected carrier and flow pipes, and the separating elements; and 
 forming a device within the double-walled pipe for arresting longitudinal propagation of buckling of the outer carrier pipe, by:
 placing at least one pair of sealing blocks axially spaced apart between the outer wall of the flow pipe and the inner wall of the carrier pipe; 
 the sealing blocks having a first circumferentially extending face and a second radially opposite face, the faces being dimensioned to be in contact respectively with the outer and inner walls of the flow pipe and the carrier pipe, to define a sealed annular region within the annular space; 
 spacing the sealing blocks so that the axial length of the annular region is at least equal to 0.5 times the external diameter of the carrier pipe, but occupies substantially less than the entire annular space; 
 placing a curable compound in the annular region; and 
 curing the compound in the annular region; 
 winding the pipe onto a receiving reel after placing the curable compound in the annular region; 
 transporting the reel carrying the pipe to a site for use of the pipe, and unwinding the wound pipe from the reel at the site for use. 
 
 
   
   
     21. The method of  claim 20 , wherein;
 the curable compound is introduced into the annular region while the pipe is on land, 
 the receiving reel is located on a pipe-laying vessel, and 
 the wound reel is transported on the vessel to the site for laying of the pipe.